You may not like to hear it since it's not a fast path, but the best way to find a quality cofounder is probably to work in an established startup; especially y

You may not like to hear it since it's not a fast path, but the best way to find a quality cofounder is probably to work in an established startup; especially you start there early and get through its growth stages. You'll not just meet brilliant coworkers, but also ones who specifically thrive in startups; and when that company grows to a certain size, they'll itch for the small startup days again and want to start something themselves. This path would take you a good few years before you get to cofound your own startup with partners, but it's probably one of the best paths.